Circulator
A circulator passes light from port 1 to port 2, and from port 2 to port 3. It separates the light going out to something from what comes back, as when reading a Bragg grating's reflection.
Ports
Ports 1, 2 and 3.
The model
Forward, round the circulator, the light has an amplitude \(t = 10^{-\ell/20}\) for an insertion loss \(\ell\) (dB). Backwards, it leaks at the isolation \(X\) (dB):
\[\mathbf S_{12} = \mathbf S_{23} = t\,\mathbf I, \qquad \mathbf S_{21} = \mathbf S_{32} = 10^{-X/20}\,\mathbf I.\]Nothing passes between ports 3 and 1, either way: it is a three-port circulator, not a closed ring. Both polarisations are treated alike, as in a polarisation-insensitive circulator.
Settings
| Field | Default | Meaning |
|---|---|---|
loss | 0.8 | Insertion loss (dB) |
iso | 40 | Isolation (dB) |
From the tool's own tables, file format version 1: the names are those in a .jekray file.
Assumptions
- Its loss and isolation are flat in wavelength and the same for both polarisations, with no polarisation-mode dispersion.
- Light into port 3 does not go on round to port 1.